Hello World game for many game systems@Brian, I think non-trivial would be more interesting. In programming, the code for Hello World is trivial, but you use it to test that you can successfully compile and run something. I can't see what the equivalent benefit would be of a trivial port to several game systems. I've added a note in the question describing what I think the benefit of this exercise would be.

Hello World game for many game systemsI consider Zendo to be a port of Eleusis, and as I said in my answer, Eleusis seems too different from most games to be helpful for this exercise. Just my opinion, of course. I still appreciate the suggestion.